Wall function treatment for bubbly boundary layers at low void fractions

Area of Science:

• Fluid Dynamics
• Multiphase Flow

Background:

• Accurate numerical prediction of bubbly flows is crucial for many industrial applications.
• Standard models often struggle with the complexities of bubbly boundary layers.
• The influence of lower boundary conditions on bubbly flow simulations requires further investigation.

Purpose of the Study:

• To evaluate the impact of different lower boundary condition treatments on numerical predictions of bubbly flows.
• To compare a new analytical wall function with a previous formulation.
• To refine turbulence modeling for bubbly flows.

Main Methods:

• Utilized a modified k-e turbulence model.
• Employed a linear superposition hypothesis for bubble and shear induced eddy viscosities.
• Implemented near-wall functions using a finite elements code.
• Validated numerical results against experimental data for bubbly boundary layers.

Main Results:

• The study highlights the necessity of four specific corrections to the standard single-phase k-e model for bubbly flows.
• The new analytical solution for wall functions shows promise in predicting bubbly boundary layers.
• Differences in boundary condition treatments significantly influence numerical predictions.

Conclusions:

• The choice of lower boundary condition treatment is critical for accurate bubbly flow simulations.
• The modified k-e model with proposed corrections offers improved predictions for bubbly boundary layers.
• Further research into analytical wall functions can enhance multiphase flow modeling.